were formerly construed, it would not have been enough to allege that the plaintiff’s goods were damaged by the defendant’s negligence. 2 These troubles had been got over by the well-known words, super se assumpsit, which will be explained later.  Assumpsit did not for a long time become an independent action of contract, and the allegation was simply the inducement to an action of tort.  The ground of liability was that the defendant had started upon the undertaking, so that his negligent omission, which let in the damage, could be connected with his acts as a part of his dealing with the thing. 3 We shall find Lord Holt recognizing this original purport of assumpsit when we come to Coggs v.  Bernard.  Of course it was not confined to cases of bailment.

But there was another way besides this by which the defendant could be charged with a duty and made liable [184] in case, and which, although less familiar to lawyers, has a special bearing on the law of carriers in later times.  If damage had been done or occasioned by the act or omission of the defendant in the pursuit of some of the more common callings, such as that of a farrier, it seems that the action could be maintained, without laying an assumpsit, on the allegation that he was a “common” farrier. 1 The latter principle was also wholly independent of bailment.  It expressed the general obligation of those exercising a public or “common” business to practise their art on demand, and show skill in it.  “For,” as Fitzherbert says, “it is the duty of every artificer to exercise his art rightly and truly as he ought.” 2

When it had thus been established that case would lie for damage when occasioned by the omission, as well as when caused by the act, of the defendant, there was no reason for denying it, even if the negligent custody had resulted in the destruction of the property. 3 From this it was but a step to extend the same form of action to all cases of loss by a bailee, and so avoid the defendant’s right to wage his law.  Detinue, the primitive remedy, retained that mark of primitive procedure.  The last extension was made about the time of Southcote’s Case. 4 But when the [185] same form of action thus came to be used alike for damage or destruction by the bailee’s neglect and for loss by a wrong-doer against whom the bailee had a remedy over, a source was opened for confusion with regard to the foundation and nature of the defendant’s duty.

In truth, there were two sets of duties,—­one not peculiar to bailees, arising from the assumpsit or public calling of the defendant, as just explained; the other, the ancient obligation, peculiar to them as such, of which Southcote’s Case was an example.  But any obligation of a bailee might be conceived of as part of a contract of bailment, after assumpsit had become appropriated to contract, the doctrine of consideration had been developed, (both of which had happened in Lord Coke’s time,) it seemed